Le Chatelier's Principle Research Articles

Landau and Lifshitz’ Formulation of Le Chatelier’s Principle: An Insight into Symbiosis?

A correspondence allows application of Landau and Lifshitz' formulation of Le Chatelier's principle from statistical physics to a simple 2-D model of biological symbiosis. The insight: symbionts stabilize the occupation of narrow peaks on fitness landscape.

Theoretical aspects of self-assembly of proteins: A Kirkwood-Buff-theory approach

A new approach to the problem of self-assembly of proteins induced by temperature, pressure, or changes in solute concentration is presented. The problem is formulated in terms of Le Chatelier principle, and a solution is sought in terms of the Kirkwood-Buff theory of solutions. In this article we focus on the pressure and solute effects on the association-dissociation equilibrium. We examine the role of both hydrophobic and hydrophilic effects. We argue that the latter are more important than the former. The solute effect, on the other hand, depends on the preferential solvation of the monomer and the aggregate with respect to solvent and co-solvent molecules. An experimental approach based on model compounds to study these effects is suggested.

Adaptive machine and its thermodynamic costs

We study the minimal thermodynamically consistent model for an adaptive machine that transfers particles from a higher chemical potential reservoir to a lower one. This model describes essentials of the inhomogeneous catalysis. It is supposed to function with the maximal current under uncertain chemical potentials: if they change, the machine tunes its own structure fitting it to the maximal current under new conditions. This adaptation is possible under two limitations. (i) The degree of freedom that controls the machine's structure has to have a stored energy (described via a negative temperature). The origin of this result is traced back to the Le Chatelier principle. (ii) The machine has to malfunction at a constant environment due to structural fluctuations, whose relative magnitude is controlled solely by the stored energy. We argue that several features of the adaptive machine are similar to those of living organisms (energy storage, aging).

Exact solution of the unsteady Krook kinetic model and nonequilibrium thermodynamic study for a rarefied gas affected by a nonlinear thermal radiation field

A development of the previous paper (J. Non-Equilib. Thermodyn. 36, 75 (2011)) is introduced. The nonstationary Krook kinetic equation model for a rarefied gas affected by nonlinear thermal radiation field is solved, instead of the stationary equation. In a frame comoving with the fluid, analytically the Bhatnager–Gross–Krook model kinetic equation is applied. The travelling wave solution method is used to get the exact solution of the nonlinear partial differential equations. These equations were produced from applying the moment method to the unsteady Boltzmann equation. Now we should solve nonlinear partial differential equations in place of nonlinear ordinary differential equations, which represent an arduous task. The unsteady solution gives the problem a great generality and more applications. The new problem is investigated to follow the behavior of the macroscopic properties of the gas, such as the temperature and concentration. They are substituted into the corresponding two-stream maxiwallian distribution functions permitting us to investigate the nonequilibrium thermodynamic properties of the system (gas particles + the heated plate). The entropy, entropy flux, entropy production, thermodynamic forces, and kinetic coefficients are obtained. We investigate the verification of the Boltzmann H-theorem, Le Chatelier principle, the second law of thermodynamic and the celebrated Onsager's reciprocity relation for the system. The ratios between the different contributions of the internal energy changes based upon the total derivatives of the extensive parameters are estimated via the Gibbs formula. The results are applied to helium gas for various radiation field intensities due to different plate temperatures. Graphics illustrating the calculated variables are drawn to predict their behavior and the results are discussed.

Equilibrium composition and initial rate of the reversible solid phase reaction in the system Na2CO3-BaSO4-Na2SO4-BaCO3

The results of experimental study of reversible solid-state reaction Na2CO3 + BaSO4 = Na2SO4 + BaCO3 were considered. The equilibrium composition of the mixture at 550 and 600°C with 10 different initial ratios of the reactants, and the initial rate of the process were determined. The role of the Le Chatelier principle in the analysis of the thermodynamic state of the reagents was considered. The thermodynamic equilibrium constant was found from the data on the dependence of concentration equilibrium constants on the composition and the results of X-ray phase analysis using regular solution theory.

Oxygen Concentration Control of Dopamine-Induced High Uniformity Surface Coating Chemistry

Material surface engineering has attracted great interest in important applications, including electronics, biomedicine, and membranes. More recently, dopamine has been widely exploited in solution-based chemistry to direct facile surface modification. However, unsolved questions remain about the chemical identity of the final products, their deposition kinetics and their binding mechanism. In particular, the dopamine oxidation reaction kinetics is a key to improving surface modification efficiency. Here, we demonstrate that high O(2) concentrations in the dopamine solution lead to highly homogeneous, thin layer deposition on any material surfaces via accelerated reaction kinetics, elucidated by Le Chatelier's principle toward dopamine oxidation steps in a Michael-addition reaction. As a result, highly uniform, ultra-smooth modified surfaces are achieved in much shorter deposition times. This finding provides new insights into the effect of reaction kinetics and molecular geometry on the uniformity of modifications for surface engineering techniques.

New Process Concepts for CO2 Capture based on Precipitating Amino Acids

This work summarises the results of the design of novel separation processes for CO2 removal from flue gas based on precipitating amino acid solvents. The processes here described (DECAB, DECAB Plus and pH-swing) use a combination of enhanced CO2 absorption (based on the Le Chatelier's principle) and / or enhanced CO2 desorption (based on pH-shift), which contribute substantially to the reduction of regeneration energy. An evaluation of these processes has been developed based on literature data, thermodynamic principles and experimental data. As solvent example, the potassium salt of taurine was selected. The results show that these processes are environmentally friendly (no emissions to the air, lower ecotoxicity) and have lower energy consumption than conventional MEA. The DECAB Plus process has been identified as the option with lower energy consumption (66% of conventional MEA- ie ca 2.4 GJ/t CO2). This study has established the potential of precipitating amino acids as an energy effective alternative to alkanol amines. The future work will focus on determining the cost of CO2 avoidance and investigating other solvents that will further lead to benefits over conventional processes.

Facile template-free synthesis of porous g-C3N4 with high photocatalytic performance under visible light

Porous g-C3N4 was synthesized by a facile template-free method to control the reaction of polymer according to Le Chatelier's principle. The resulting porous g-C3N4 material has high Brunauer–Emmett–Teller (BET) surface area (201–209 m2 g−1) and large pore volume (0.50–0.52 m3 g−1), and shows a ten times enhanced photocatalytic activity for methyl orange (MO) photodegradation under visible light (λ > 420 nm) irradiation.

Theoretical aspects of pressure and solute denaturation of proteins: A Kirkwood-buff-theory approach

A new approach to the problem of pressure-denaturation (PD) and solute-denaturation (SD) of proteins is presented. The problem is formulated in terms of Le Chatelier principle, and a solution is sought in terms of the Kirkwood-Buff theory of solutions. It is found that both problems have one factor in common; the excluded volumes of the folded and the unfolded forms with respect to the solvent molecules. It is shown that solvent-induced effects operating on hydrophilic groups along the protein are probably the main reason for PD. On the other hand, the SD depends on the preferential solvation of the folded and the unfolded forms with respect to solvent and co-solvent molecules.

Bioleaching of ilmenite and basalt in the presence of iron-oxidizing and iron-scavenging bacteria

AbstractBioleaching has been suggested as an alternative to traditional mining techniques in extraterrestrial environments because it does not require extensive infrastructure and bulky hardware. In situ bioleaching of silicate minerals, such as those found on the moon or Mars, has been proposed as a feasible alternative to traditional extraction techniques that require either extreme heat and/or substantial chemical treatment. In this study, we investigated the biotic and abiotic leaching of basaltic rocks (analogues to those found on the moon and Mars) and the mineral ilmenite (FeTiO3) in aqueous environments under acidic (pH ∼ 2.5) and circumneutral pH conditions. The biological leaching experiments were conducted using Acidithiobacillus ferrooxidans, an iron (Fe)-oxidizing bacteria, and Pseudomonas mendocina, an Fe-scavenging bacteria. We found that both strains were able to grow using the Fe(II) derived from the tested basaltic rocks and ilmenite. Although silica leaching rates were the same or slightly less in the bacterial systems with A. ferrooxidans than in the abiotic control systems, the extent of Fe, Al and Ti released (and re-precipitated in new solid phases) was actually greater in the biotic systems. This is likely because the Fe(II) leached from the basalt was immediately oxidized by A. ferrooxidans, and precipitated into Fe(III) phases which causes a change in the equilibrium of the system, i.e. Le Chatelier's principle. Iron(II) in the abiotic experiment was allowed to build up in solution which led to a decrease in its overall release rate. For example, the percentage of Fe, Al and Ti leached (dissolved + reactive mineral precipitates) from the Mars simulant in the A. ferrooxidans experimental system was 34, 41 and 13% of the total Fe, Al and Ti in the basalt, respectively, while the abiotic experimental system released totals of only 11, 25 and 2%. There was, however, no measurable difference in the amounts of Fe and Ti released from ilmenite in the experiments with A. ferrooxidans versus the abiotic controls. P. mendocina scavenged some Fe from the rock/mineral substrates, but the overall amount of leaching was small (<2% of total Fe in rocks) when compared with the acidophilic systems. Although the mineralogy of the tested basaltic rocks was roughly similar, the surface areas of the lunar and Mars simulants varied greatly and thus were possible factors in the overall amount of metals released. Overall, our results indicate that the presence of bacteria does not increase the overall silica leaching rates of basaltic rocks; however, the presence of A. ferrooxidans does lead to enhanced release of Fe, Al and Ti and subsequent sequestration of Fe (and other metals) in Fe(III)-precipitates.

Selective Nitride Etch by Using Fluorides in High Boiling Point Solvent

Conventional wet etching techniques for selectively removing silicon nitride (Si3N4) have utilized hot (approximately 145-180°C) aqueous phosphoric acid (H3PO4) solutions (often referred to as hot phos). The typical Si3N4:SiO2 selectivity is about 40:1 when using 85% fresh hot phosphoric acid. Advantageously, as the nitride layer is removed, hydrated silicon oxide forms and dissolves in the etchant. Consistent with Le Chatelier principle, this inhibits the additional removal of silicon oxide from the device surface; thus selectivity gradually increases with use [.

Cellular Strategies for Regulating Functional and Nonfunctional Protein Aggregation

SummaryGrowing evidence suggests that aggregation-prone proteins are both harmful and functional for a cell. How do cellular systems balance the detrimental and beneficial effect of protein aggregation? We reveal that aggregation-prone proteins are subject to differential transcriptional, translational, and degradation control compared to nonaggregation-prone proteins, which leads to their decreased synthesis, low abundance, and high turnover. Genetic modulators that enhance the aggregation phenotype are enriched in genes that influence expression homeostasis. Moreover, genes encoding aggregation-prone proteins are more likely to be harmful when overexpressed. The trends are evolutionarily conserved and suggest a strategy whereby cellular mechanisms specifically modulate the availability of aggregation-prone proteins to (1) keep concentrations below the critical ones required for aggregation and (2) shift the equilibrium between the monomeric and oligomeric/aggregate form, as explained by Le Chatelier’s principle. This strategy may prevent formation of undesirable aggregates and keep functional assemblies/aggregates under control.

Analysis of DNA-guided self-assembly of microspheres using imaging flow cytometry.

Imaging flow cytometry was used to analyze the self-assembly of DNA-conjugated polystyrene microspheres. This technique enables quantitative analysis of the assembly process and thereby enables detailed analysis of the effect of structural and process variables on the assembly yield. In a demonstration of the potential of this technique, the influence of DNA strand base pair (bp) length was examined, and it was found that 50 bp was sufficient to drive the assembly of microspheres efficiently, forming not only dimers but also chainlike structures. The effect of stoichiometry on the yield was also examined. The analysis demonstrated that self-assembly of 50 bp microspheres can be driven nearly to completion by stoichiometric excess in a manner similar to Le Chatelier's principle in common chemical equilibrium.

A numerical study of pellets having both catalytic- and capture properties for SE-SMR process: Kinetic- and product layer diffusion controlled regimes

Sorption enhanced steam methane reforming (SE-SMR) is a promising process for the production of H2. The in situ removal of CO2 in the steam methane reforming (SMR) process shifts the reaction equilibrium according to the Le Chatelier's principle towards higher H2 production. Most of the earlier studies worked on the SE-SMR process using two different pellets (2-P): one for the reforming catalyst and the other one for the CO2 adsorbent. In this study, we propose a novel pellet design where both the catalyst and sorbent are put together in a support (1-P). In the 1-P system, the produced CO2 molecules due to the reforming reactions will be captured by the sorbent inside the pellet. Whereas in the 2-P system, the CO2 molecules have to transported in between the pellets to be captured by the sorbent. Hence, 1-P design has less resistance for mass transfer between the catalyst and sorbent active sites. In this study, the internal mass transport limitations of the 1-P design for the SE-SMR process have been investigated.The dusty gas multicomponent mass diffusion pellet model formulated for the SE-SMR process describes the evolution of species mole fractions, pressure, total concentration, temperature, fluxes, and convection within the voids of the porous pellet. The internal effectiveness factors of the SE-SMR process have been calculated for the SE-SMR process. The effective diffusivities are described according to the parallel pore- and random pore models. The carbonation reaction in the SE-SMR process is a gas–solid reaction system, which generally follows one out of two controlled regimes, namely the kinetic- and product layer diffusion (PLD) controlled regimes. A mathematical model based on the grain model was applied modelling the carbonation reaction. The change in pellet void-fraction due to the formation of the solid CaCO3, the diffusion of gaseous phase through the product layer, the structural changes of the spherical grains by the inclusion of variable diffusion coefficient and multiple carbonation/calcination cycles were considered in the pellet model. The effect of pellet diameter on the carbonation reaction rate is investigated to observe the complex mechanism of gas–solid reaction system.The 1-P performance is promising compared to the conventional 2-P design. Further, the reduction in void-fraction with the CaO conversion, product layer diffusion, pellet diameter and multiple cycles are all important effects in the SE-SMR process because these mechanisms influence on the reaction rate, capture capacity, and the effectiveness factors.

METHODOLOGY FOR PREDICTING CHEMICAL EQUILIBRIA SHIFT: CHANGING SYSTEM COMPOSITION AT CONSTANT TEMPERATURE

The subject of perturbations of an equilibrium system and the direction in which it shifts as it moves towards a new equilibrium is an important aspect of general and physical chemistry courses. Of particular importance is students' ability to predict the effects of changing conditions on the position of chemical equilibrium. On a teaching context, the Le Chatelier's principle is still used as an infallible principle without showing its limitations which can lead to very important misconceptions. In this paper it is presented a teaching methodology to avoid the Le Chatelier’s qualitative rule. This methodology is based on extent of reaction, affinity of reaction, and thermodynamic potentials. Focusing on the effects of adding more reactants or products on chemical equilibrium (at constant temperature), our proposal gives the mathematical expression of the variation of the extent of reaction with the infinitesimal variation in the number of moles, and it allows to make exact predictions about the evolution of a perturbed chemical equilibrium system.

Rate of return regulation and the Le Chatelier principle

This paper examines whether rate-of return regulation alters the input quantities firms use to produce their selected output level when the corresponding input prices change, in a manner similar to the Le Chatelier principle. More specifically, would the change in a rate regulated firm’s input quantity due to a change in its input price be less price elastic than the unregulated firm’s change in the input quantity due to a change in its input price. We follow Fare and Logan (1986), Nelson and Wohar (1983) in estimating a rate regulated cost function and capital input share system of equations. Using a 1992–2000 panel of 34 US major investor-owned electric utilities, empirical results indicate that the regulated own-input price elasticities of demand for labor and fuel are less price elastic than their corresponding unregulated own-input price elasticities of demand (a Le Chatelier principle type effect). Having a fuel clause (1) reduces the firm’s willingness to substitute from fuel to either non-fuel (capital, labor) input when the price of fuel rises, and (2) enhances the firm’s willingness to substitute from non-fuel inputs to fuel when the price of non-fuel inputs rises.

Ammonothermal Synthesis of Alkali N,N′‐Bis(aminocarbonyl)phosphorodiamidates M[PO2(NHCONH2)2] (M = Na, K, Rb)

AbstractCompounds M[PO2(NHCONH2)2] with M = Na, K, and Rb, which are the salts of N,N′‐bis(aminocarbonyl)phosphorodiamidic acid, were synthesized by ammonolysis of the corresponding alkali biuretooxophosphates M[PO2(NH)3(CO)2] (M = Na, K, Rb) at 350 °C and 120–150 bar in an autoclave. The structures were solved by single‐crystal X‐ray diffraction and exhibit 3D frameworks in which N,N′‐bis(aminocarbonyl)phosphorodiamidate ions connect the corresponding alkali ions. The thermal behavior was investigated by combined thermogravimetric (TG) and differential thermal analysis (DTA) as well as temperature‐dependent powder X‐ray diffraction to evaluate applicability of the alkali N,N′‐bis(aminocarbonyl)phosphorodiamidates as precursors for the synthesis of CNP(O) networks. In this context, the concept of Le Chatelier's principle for the hindrance of premature decomposition by applying elevated pressure was examined.

LeChatelier Principle and the Effects of Trade Policy under Induced Innovation

This paper explores the effects of trade policy under induced innovation in general equilibrium. The analysis considers the effects of discrete changes in tariffs and import quotas, allowing for heterogeneous technologies among firms. The interactions between induced innovation and the effects of trade policy give a set of “LeChatelier effects” comparing short run versus long run market equilibrium. We investigate how induced innovation can reduce the adverse effects of tariffs on trade, and influence the effects of quotas on corresponding quota rents. The analysis presents new LeChatelier results that apply globally, i.e. under any discrete change in trade policy.

Le Chatelier's principle in replicator dynamics

The Le Chatelier principle states that physical equilibria are not only stable, but they also resist external perturbations via short-time negative-feedback mechanisms: a perturbation induces processes tending to diminish its results. The principle has deep roots, e.g., in thermodynamics it is closely related to the second law and the positivity of the entropy production. Here we study the applicability of the Le Chatelier principle to evolutionary game theory, i.e., to perturbations of a Nash equilibrium within the replicator dynamics. We show that the principle can be reformulated as a majorization relation. This defines a stability notion that generalizes the concept of evolutionary stability. We determine criteria for a Nash equilibrium to satisfy the Le Chatelier principle and relate them to mutualistic interactions (game-theoretical anticoordination) showing in which sense mutualistic replicators can be more stable than (say) competing ones. There are globally stable Nash equilibria, where the Le Chatelier principle is violated even locally: in contrast to the thermodynamic equilibrium a Nash equilibrium can amplify small perturbations, though both types of equilibria satisfy the detailed balance condition.

Why alite stops hydrating below 80% relative humidity

It has been observed that the hydration of cement paste stops when the relative humidity drops below about 80%. A thermodynamic analysis shows that the capillary pressure exerted at that RH shifts the solubility of tricalcium silicate, so that it is in equilibrium with water. This is a reflection of the chemical shrinkage in this system: according to Le Chatelier's principle, since the volume of the products is less than that of the reactants, a negative (capillary) pressure opposes the reaction.